The present invention relates to a liquid crystal display device, and more particularly, to a technique for fixing a liquid crystal display panel and a backlight unit.
Referring to FIG. 5, a generally employed liquid crystal display device is configured to install a drive circuit DR at a lower side of a liquid crystal display panel LCD shown in the drawing, and to connect a flexible wiring substrate FPC at a position closer to an edge side of the liquid crystal display panel LCD than the drive circuit DR. A double-sided tape TP is attached to a back surface of the liquid crystal display panel LCD while surrounding a display region AR so as to fix the liquid crystal display panel LCD and a backlight unit BU as a light source.
More specifically, as shown in FIG. 6 (sectional view taken along line B-B′ of FIG. 5) and FIG. 7 (sectional view taken along line C-C′ of FIG. 5), the double-sided tape TP is used to bond the upper surface of a frame-like mold member MD which is formed to surround the light guide plate LG and the optical sheet OS to the back surface of a first substrate SUB1 so that the backlight unit BU is fixed to the back surface of the first substrate SUB1 . A reflection sheet RF provided on the back surface of the light guide plate LG has a size sufficient to reach the mold member MD, having the peripheral edge fixed to the back surface of the mold member MD with the double-sided tape TP. Surfaces of the first substrate SUB1 and a second substrate SUB2 , which are not in contact with the liquid crystal layer, have polarizing plates POL1 and POL2, respectively. The liquid crystal display panel LCD and the mold member MD are bonded via the polarizing plate POL1 by using the double-sided tape TP.
The liquid crystal display device disclosed in JP-A-2007-163556 is configured to use the double-sided tape for fixing the upper surface of the backlight unit to the back surface of the liquid crystal display panel. Especially, such liquid crystal display device has a large gap between the side edge of the lower polarizing plate and the side edge of the glass substrate so that the double-sided tape is bonded to the resultant gap.
The mobile information terminal such as the mobile phone is demanded to further improve the display performance such as an increase in the number of pixels, and expansion of the display screen while keeping a limited casing size. The liquid crystal display device to be installed in the mobile information terminal has been required to further reduce the width of the frame region as the peripheral area of the display region AR as well as the increased number of pixels. Recently, the liquid crystal display device has been demanded to set the width of the frame region to 0.8 mm or 0.6 mm.
The generally employed liquid crystal display device is configured to use the double-sided tape TP which adheres to the front surface of the mold member MD opposite the frame region of the liquid crystal display panel for fixing the backlight unit BU to the back surface of the liquid crystal display panel LCD. For that reason, when the frame region width is further reduced, the width of the double-sided tape TP for fixing the liquid crystal display panel LCD to the mold member MD is reduced as well, as clearly shown in the sectional views of FIGS. 6 and 7. In this case, the bonded area between the mold member MD and the double-sided tape TP, and the bonded area between the liquid crystal display panel LCD and the double-sided tape TP are decreased, respectively. Especially, the bonded area of the side section where the drive circuit DR is not installed as shown in FIG. 7 is significantly decreased. It is therefore difficult to fix those elements with a predetermined strength. Accordingly, development of technique for fixing the liquid crystal display panel LCD and the backlight unit BU without using the double-sided tape TP has been much needed.